Zombie-like honeybees infested by fly parasite

Potential threat to colonies across North America

Honeybees infested with a fly parasite abandon their hives and die after a bout of disoriented 'zombie'-like behavior, according to research from San Francisco State University. (Linda Davidson/The Washington Post/Associated Press)

A fly parasite that latches onto honeybees causing them to abandon their hives and die after a bout of disoriented zombie-like behaviour could be a potential threat to honeybee colonies across North America, according to researchers at San Francisco State University.

Studying the phenomenon may help scientists learn about colony collapse disorder (CCD), SF State biology professor John Hafernik wrote in the journal PLoS ONE published Tuesday.

So far, the fly parasite called Apocephalus borealis has only been found in honeybee hives in California and South Dakota. The fly deposits its eggs into a bee's abdomen. After being parasitized by the fly, the bees abandon their hives to congregate near lights.

"When we observed the bees for some time — the ones that were alive — we found that they walked around in circles, often with no sense of direction…. It really painted a picture of something like a zombie," said co-researcher Andrew Core.

After about seven days, fly larvae push their way out from between the bee's head and thorax. Usually bees just sit in one place, sometimes curling up before they die.

Bees that left the hives at night were more likely to have the parasite than those that foraged during the day. Genetic testing of parasitized hives showed that both bees and flies were often infected with a deformed wing virus and a fungus called Nosema ceranae.

Pushed out by mates?

Some researchers have pointed to the fungus and virus as the potential catalysts in colony collapse disorder. Hive abandonment is the primary characteristic of the disorder.

Hafernik said the next step is to determine how the parasite is affecting bees' behavior; for example, whether the fly somehow interferes with the bees' "clock genes" that help them keep a normal day-night rhythm.

It’s also not clear whether the bees leave the hive of their own accord or are pushed out by their mates.

"A lot of touching and tasting goes on in a hive and it's certainly possible that their co-workers are finding them and can tell that there’s something wrong with them," Hafernik said.

Researchers aren't sure how to prevent the parasitization because it's not clear where the flies are latching onto the bees. It's likely that it's happening when the bees are foraging because flies aren’t hanging around the beehives, said Hafernik.

Genetic analysis of the parasites confirmed they are the same flies that have been affecting bumblebees.